Our preliminary studies show that clonally derived AXC/SSh rat prostate cancer cells secrete growth promoting activity which has properties expected of polypeptides. Our data also indicate that growth factor production and the ability of cells to respond to elaborated mitogens may be cell line specific. We propose a series of studies to identify growth factors elaborated by AXC/SSh rat prostate cancer cells and to define action of individualized mitogens in rat prostate cancer cells. Studies are performed using AXC/SSh rat prostate cancer cell lines C3 and T5 which show the greatest apparent differences. The hypothesis that mitogen production by clonally derived rat prostate cancer cells is cell line specific will be tested. Heparin-Sepharose and gel permeation chromatography will be used to individualize elaborated mitogens and similarity to prototypic growth factors will be assessed by biologic assays. Individualized growth factors will be purified to homogeneity with precedence given to prostate mitogens having properties differing from those of prototypic growth factors. Purified mitogens will be characterized by performing biologic and physical assessments, including amino acid analyses. The hypothesis that elaborated mitogens act as autocrine or paracrine modulators of rat prostate cancer cell proliferation will be tested. Individualized prostate mitogens will be assessed for ability to affect proliferation of prostate cancer cells. Synergistic or antagonistic effects will be assessed using a mitogen assay based on 3H-thymidine incorporation. The hypothesis that inability of cells to respond to an elaborated mitogen is due to failure of receptor mediated processes will be tested by assessment for functional growth factor receptors. Content will be evaluated by saturation analysis protocols and apparent molecular weight will be defined by receptor-mitogen cross-linking and subsequent acrylamide gel size fractionation. Functional status of receptors will be assessed by defining mitogen mediated receptor phosphorylation.